Electrical and Switching Phenomenon of Se₈₀Ge_20−x Cd _x (0 ≤ x ≤ 12 at.%) Amorphous System

Abstract

Se₈₀Ge_20−x Cd _x (0 ≤ x ≤ 12 at.%) compositions were prepared by the conventional melt quenching technique. Thin films with different thicknesses (200–620 nm) were deposited by thermal evaporation technique. Energy dispersive x-ray spectroscopy technique showed that the films are nearly stoichiometric. X-ray diffraction (XRD) patterns indicate that the films are in amorphous state. The DC conductivity and switching properties were investigated in the temperature range (293–393 K) below the corresponding glass transition temperature. The obtained results of DC conductivity showed that it increases with increasing Cd content in the considered system as well as with film thickness through the studied range of thickness. The conduction activation energy has two values, ΔE _σ1 and ΔE _σ2, indicating the presence of two different conduction mechanisms through the studied range of temperature. The obtained results of the temperature dependence of DC conductivity are explained in accordance with the Mott and Davis model for electrical conduction. The current–voltage (I–V) characteristic curves were studied for the investigated samples and found to be typical for a memory switch. The mean value of the threshold voltage $\overline{{V}}_{\rm{th}}$ was found to increase linearly with film thickness and decrease exponentially with temperature in the investigated ranges of thickness and temperature. The threshold voltage activation energy ε _th for the investigated samples was calculated from the corresponding temperature dependence of $\overline{{V}}_{\rm{th}}$. The switching phenomenon observed in these films is explained in accordance with the electrothermal effect initiated by Joule heating for the switching process. The effect of Cd content on the studied parameters was also investigated.